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用固相反应方法制备了Y_(1-x)Ca_xBa_2Cu_3O_y(x=0.0,0.02,0.05,0.10,0.15,0.20,0.50)系列样品,发现超导转变温度随x增加而呈线性下降。粉末x-射线衍射结果表明,在x≤0.15范围内,体系呈现出很好的正交单相性,晶格参数无明显变化。用碘滴定方法测量了体系的氧含量,发现随着x的增加,Cu的平均价态降低,氧含量减少。把上述结果同Y_(1-x)Pr_xBa_2Cu_3O_y作比较,表明氧含量和Cu的平均价态均不是决定Tc的直接因素。讨论了氧含量改变的可能位置和引起超导电性发生变化的原因。
The samples of Y_ (1-x) Ca_xBa_2Cu_3O_y (x = 0.0,0.02,0.05,0.10,0.15,0.20,0.50) were prepared by the solid-state reaction method and found that the superconducting transition temperature decreased linearly with the increase of x. The results of powder x-ray diffraction show that the system exhibits good orthogonality in the range of x≤0.15, and the lattice parameter has no obvious change. The iodine titration method was used to measure the oxygen content of the system. It was found that with the increase of x, the average valence of Cu decreased and the oxygen content decreased. Comparing the above results with Y_ (1-x) Pr_xBa_2Cu_3O_y indicates that the oxygen content and the average valence of Cu are not the direct factors that determine Tc. Discussed the possible changes in the oxygen content and the possible causes of superconductivity changes.